1. Field of the Invention
The present invention relates to a load port for semiconductor manufacturing equipment used in the production of semiconductors, semiconductor devices, and the like. This application is based on the patent application No. Hei 10-91972, filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
In order to manufacture high quality semiconductor devices in an economical manner, there has been a trend towards increasing the size of the wafer diameter. For example, a front-opening unified pod (FOUP) type carrier 11, shown in FIG. 7 (the embodiment in the figure displays a FOUP carrier with its cover removed), an open cassette (OC) type carrier 11, shown in FIG. 8, and the like, are being used as carriers for transporting wafers in semiconductor manufacturing equipment which handle wafers possessing diameters greater than 300 mm.
The peripheral structure of a load port in conventional semiconductor manufacturing equipment is typically described in FIG. 9. In FIG. 9, a wafer 12, accommodated in a carrier 11 for wafers (hereinafter, referred to as carrier 11), such as an FOUP carrier shown in FIG. 7, and the like, is transported to a load port for processing wafers in semiconductor manufacturing equipment 13 (hereinafter, referred to as equipment 13), either manually or by an automated transporter, and loaded onto a movable, carrier base 14, which is stationed at the load port. Additionally, an opening 16 for the wafer 12 is provided in the equipment 13. The opening 16 is usually closed with a cover 15 (described below). When the cover 15 is opened, it is possible to move the wafer 12 in and out between the carrier 11 and the equipment 13 through the aforementioned opening 16, or alternatively store the wafer 12 together with the carrier 11 inside the equipment 13 through the opening 16.
The carrier 11, which has been transported to the load port, is loaded onto a carrier base 14, which has been positioned in front of the opening 16. This carrier base 14 can move further away from, as well as towards the opening 16. The carrier 11 is loaded onto the carrier base 14 at a position that is a short distance away from opening 16, and is transported towards the opening 16, together with the carrier base 14. In general, with respect to a FOUP carrier, the cover 15 of the opening 16 is designed to open with carrier 11, loaded onto the carrier base 14, pushed against the front surface of the equipment 13. Thereafter, the wafer 12 housed within the carrier 11 is removed.
The force of pushing the carrier 11 against the front surface of the equipment 13 is set to a minimum. However, since a positive pressure exists within the equipment 13 to prevent dust from entering, the force of carrier exerted against the front surface of the equipment must be at least large enough to overcome this pressure. For example, if the equipment 13 possesses an inner capacity of 50 mm of water, and a FOUP (i.e., carrier 11), accommodating 25 sheets of wafers 12, possesses a projected surface area against the equipment 13 of 300 mm.times.350 mm, a force of at least 5.25 kg is required to push the carrier 11 against the equipment 13. Furthermore, in the case when, in order to prevent oxidation of the wafer 12, the interior of the equipment 13 is filled with an inert gas such as nitrogen, argon, dry air, or the like, a sealing material is required in between the equipment 13 and the carrier 11 to prevent this gas from leaking. In such a case, the carrier 11 pushes up against the equipment 13 through this sealing material, and thus a greater force is required.
Thus, in order to obtain the aforementioned required force, a device that possesses the capability of generating this force is used as an actuator for moving the carrier 11. Therefore, in the case when the carrier 11 is transported towards the opening 16, the actuator continuously operates, driving the carrier 11 against the opening 16 with the required force.
However, the aforementioned force is actually required only during the final step, and is not necessary throughout the entire process. Moreover, when the carrier 11 is transported together with the carrier base 14 using an excessively large force, extreme caution must be maintained during operation, as a substantial risk of injury exists via a projection or the like, in such cases as when a hand is caught in between the carrier 11 and the equipment 13 during transportation. In addition, for the same reasons, extreme caution must be exercised, not only while pushing the carrier 11 against the opening 16, but also when closing the opening 16 with the cover 15 using a large force.
In consideration of the above problems, it is an object of the present invention to provide a load port that possesses a highly safe structure in order to prevent injuries due to a lack of caution.